need help with heads..

[kennyhammond]

Ok I got a 90 chevy truck with a 350.. well pulled the motor because either the head gasket is bad or I ha ve a cracked head.... so for now I put a spare 305 in it to drive ....so I am left with the 350 to rebuild.... I am not wanting to spend much money if any at all...plan on making it just a little fun to drive but nothing wild...so my question is can I put the 305 heads back on and put my throttle body on it and be good and see some gains or ........ plan on a small cam change also. Any info would realy help plan to build next week
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[ctandc]

Depends.

What cc are the 350 heads? What’s the stock head gasket thickness?

Most 305 heads are 58cc combustion chambers. The majority of the TBI 350’s would have 64cc chambers. That’s all taking into account a previous owner hasn’t swapped stuff around.

If this is the case, adding the 305 heads onto the 350 will raise your compression ratio.

Just google how to measure the cc’s of your combustion chambers. Not expensive or hard. Well worth it.

Next google “Quench area for small block Chevrolets” and do some reading. Again, nothing but time and a few simple tools needed.

If it were me I’d check the 350 out before deciding on anything. Were you losing coolant? Was it mixing with oil? Was it burning coolant?

I do know I’ve bought more than my share of 87-later 350’s with “blown head gaskets” or “cracked heads” and they all turned out to have a leaking intake gasket.

Hope this helps.

[Marv D]

One of my petpeives is the 305 heads on a 350. If you want it to run a bit worse than a 305,, then it's a good move. They build compression,,but that does little for you in this day of $4 a gallon 87 octane.

The 305 was built as a EPA appeasment with torque. The small bore (even just a tad SMALLER than the original 265) long stroke (same as the 350) made decent torque to push the heavy 80's vehicles around and could be choked down (with poor heads and small throttle bodies) to get decent effeciency,, but runs out of breath around 4000rpm. What do you think is going to happen when you try to move the volume of air through them that a 350 demands????

Round-de-round guys do it so they cn support the compression required with running a BIG cam, and keeping the motor up as high as it will make power. They they will dump a copuple of weekends in to them with a air grinder and bag of tootsie-roll abrasive pads hoping they 'improve'... not 'make worse' what was a bad idea in the first place.

Without sounding like a tool.... your not wanting to spend any money,,, expect what you pay for and the 305 heads will work because you have them.

[kennyhammond]

Ok got it....don't use the 305heads....so what ideas does anyone have ..... there was water in the oil...
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[Marv D]

It's been beat to death around the inernet,,, but... from the GM production side of things....... the modern alternative to the early LT1 heads is the Vortecs.Over 10 years now after their end of production,, the stock iron vortecs are showing signs of age. It's a light weight casting to begin with,, and with poor maintenance valve guides are trashed, overheating has caused cracks, valve / seat replacment... many are not even a good doorstop any more. But in stock form they out-flowed the early duble humps and offered a chamber that held compression down in a flat top 350.

Myself I would rather spend $600 for a set of aftermarket RHS vortec heads that are 100% all new, rather than spend a couple of hundred on a used set, then $200-400 trying to refurbish them. The aftermarket (although costly) has updated the flaws found in the production castings,, better chamber, valves, guides, springs that typically will support agressive hydraulic cams, and valve guides that don't need to be machined to get over .47 lift,,,

a better head just cost more. AFR, Dart, Brodies... it's just money.

[BigDan3131]

Originally Posted by Marv D

It's been beat to death around the inernet,,, but... from the GM production side of things....... the modern alternative to the early LT1 heads is the Vortecs.Over 10 years now after their end of production,, the stock iron vortecs are showing signs of age. It's a light weight casting to begin with,, and with poor maintenance valve guides are trashed, overheating has caused cracks, valve / seat replacment... many are not even a good doorstop any more. But in stock form they out-flowed the early duble humps and offered a chamber that held compression down in a flat top 350.

Myself I would rather spend $600 for a set of aftermarket RHS vortec heads that are 100% all new, rather than spend a couple of hundred on a used set, then $200-400 trying to refurbish them. The aftermarket (although costly) has updated the flaws found in the production castings,, better chamber, valves, guides, springs that typically will support agressive hydraulic cams, and valve guides that don't need to be machined to get over .47 lift,,,

a better head just cost more. AFR, Dart, Brodies... it's just money.

The used vortecs are todays double hump heads in that you have to go thru them completely like we use to do. Their are plenty of low budget stock replacement heads that allow you to use your factory accs instead of just using the vortecs in which you have to switch out more stuff.

I like these: http://www.jegs.com/i/Dart/301/12712...09#moreDetails the price is per head but yet your getting aluminum heads instead of cast iron.

[Lower]

Those motors are known for blowing the intake gaskets. Thats probably what you would have checked first before assuming the heads

[ctandc]

Originally Posted by kennyhammond

Ok got it....don't use the 305heads....so what ideas does anyone have ..... there was water in the oil...
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See my first post. Check the intake gasket. These engine are famous for intake leaks which are misdiagnosed as head gaskets or worse.

Originally Posted by Lower

Those motors are known for blowing the intake gaskets. Thats probably what you would have checked first before assuming the heads

Guess I'm not the only one who's seen this.
Vortec heads are great. But as mentioned, they are getting older. Just like ‘double hump’ heads were touted as being great, so have Vortec heads risen. I know plenty of people who are penny wise and pound foolish when it comes to building engines. They look for a good deal on used cylinder heads, then drop them off at the machine shop, and by the time they are done, they many times end up spending more than they would have if they bought an aftermarket cylinder designed for performance.
That being said, you can still find good Vortec heads, but the best way is to find them on a running Vortec engine.
Then there is the cam lift restraint (@ .470 lift) on stock heads. You need to do some machine work, although there are some aftermarket springs that can solve this problem.
Check out what you have before you start doing anything, you might have a perfectly good engine that just needs a little work.